UDP Retransmissions
Although UDP is a connectionless protocol, applications do retransmit UDP packets. Different applications use different methods for determining retransmissions (such as timers or sequence numbers). By analyzing UDP traffic from the application perspective, Observer can determine whether a particular UDP packet was retransmitted, and displays a running count.
Further graphical analysis of where in the conversation the retransmissions are occurring can be seen by right clicking on the pair and selecting "Connection Dynamics".
Graph bars indicate the state of the conversation delay by color:
Red indicates a critical event has occurred.
Yellow indicates a marginal event has occurred.
Green indicates that the conversation's communication is within acceptable event parameters.
The color's event trigger point is defined for each application in the Expert Thresholds setup.
UDP retransmissions occur for a number of reasons, including the packet was lost, dropped or otherwise missing. The event is displayed when the percentage of UDP retransmission packets (by application and address pair) is above the critical value set in the Expert Thresholds.
Possible reasons for the event:
The receiving station was too busy to respond to the sending station.
network traffic load was so high the original packet was lost due to the high utilization.
A router dropped the packet, or was unable to forward the packet. This could be because the router is too busy, or is malfunctioning.
Bad cabling or a failing switch/hub is causing an intermittent network failure.